The present invention relates to a recording apparatus or system which is similar in some respects to the conventional ink-jet printing systems.
In general, the conventional ink-jet printing systems may be divided into the ink-on-demand type and the electrostatic deflection type. In both types, the ink drops of very small diameters are issued from the print head and steered to the desired spots on a recording sheet, thereby forming characters, patterns and the like. The ink drops are issued in general from a nozzle with an extremely fine nozzle hole, and the ink used contains solid substances. As a result, the conventional ink-jet printing systems have a serious common defect that the clogging of nozzles tends to occur very frequently. That is, in inoperative mode the ink remains in the nozzle and the ink solvent continues to evaporate, leaving the rich concentration which clogs the nozzle hole. As a result, even when the ink-jet printer is started, no ink drop can issue from the nozzle or nozzles. In order to overcome this problem, there has been proposed to use a moistening agent to the ink so as to retard its vaporization. Alternatively, there has been proposed to use a cap to close the nozzle so as to prevent the evaporation in the inoperative mode. However, these and other counter-measures have proved unsatisfactory in practice because the inherent properties of the ink used are not taken into consideration.
As a consequence, used satisfactorily in practice is the so-called ink-dot systems which use only a small number of nozzles ranging from five to seven, but it is almost not feasible to provide, instead of the prior art printing systems such as electrophotographic machines, the ink-jet printing systems which employs a large number of nozzles ranging from hundreds to thousands so as to produce the prints or copies in large size.